Our earlier work has shown that the combination of high dose radiation and hepatic arterial floxuridine (FUdR) (0.2 mg/kg/day) is among the most effective treatments for patients with localized but unresectable cancer in the liver (both primary liver cancers and cancers that have spread to the liver from the colon or rectum). The purpose of this study is to determine the maximum dose of radiation (as a function of volume of liver irradiated) that can be given safely. Radiation dose will be increased in groups of patients according to a mathematical model derived from our previous patients. We feel it is likely that if the dose can be increased safely, the tumor control and survival can be increased.